1. Field of the Invention
The present invention is related to private communications networks and more particularly, to providing call completion services between a private communications network and a public communication network.
2. Background Description
A private communications network, such as a private voice network, is a full featured telephone network. A typical private communications network may include, for example, a communications server or private branch exchange (PBX) server linking together wire connected digital phones for a particular enterprise, e.g., phones located in offices on a common campus. The digital phones may be cordless to allow some mobility within a specific local area and sometimes are Internet protocol (IP) based for easy expansion, e.g., simply by connecting extra IP phones. Private communications network users can share both data and voice based information across the private network to improve productivity.
One such feature included in a typical private communications network is the callback service. When a call does not complete, i.e., the called number is busy or the called party does not answer, the caller can request a “callback.” Thereafter, the PBX server monitors the status of the called number until a connection is deemed possible, e.g., when the called party next goes on-hook. Then, the PBX server rings the caller back and automatically connects the caller to the desired destination.
A similar service is available in some public networks between the public network telephones. In this case when a caller calls a busy destination, some public networks play an announcement to the caller such as “The party you have called is busy. For 50 cents we will continue to try this party for you and ring you when your party is available.” If such a service is unavailable, callers may resort to using an intelligent telephone that continuously redials until it completes the call. However, this wastes network resources and can be expensive for the user. “Repeat dialers” are commercially available but are illegal in some areas and can lead to additional telephone charges. Thus, all of these callback solutions can be expensive.
Call control messaging protocols have standardized between European public and private telephone networks. This protocol standardization permits using standard call control methods for callback features. However, using these protocols requires that all switching nodes (public and private) involved in the call know the special protocols. There is no such mechanism in current North American telephone systems to provide callback services in mixed private/public networks, i.e., where one party is at a public network telephone and the other is at a private network telephone.
Thus, there is a need for an improved callback service between private communications networks and public network users.